Existing roadway surfaces will typically include roadway lane demarcation markings to assist motorists for visually identifying lanes for controlling and directing traffic. In many cases the roadway markings are placed directly onto the roadway top surface and usually consist of paint of various colors such as white or yellow for asphalt-covered roadways, or white or yellow onto a black painted background to accentuate contrast between the roadway surface and mark (used especially on lighter-colored concrete roadways). In other cases, roadway markings may be placed in grooves previously milled into the roadway surface.
The visible contrast between the roadway surface and the roadway mark is an important consideration for drivers of vehicles to be able to quickly and reliably discern the correct traffic lane under both daytime and nighttime, dry and wet, roadway driving conditions.
Different materials have been perfected for roadway markings. The most common roadway marking material is in liquid form (generically called “paint”) which is sprayed onto the roadway surface from a forward-moving paint vehicle along a desired roadway mark path. The liquid material then dries, cures or solidifies forming a dry and semi-permanent roadway marking. The applied thickness of the liquid marking material may be approximately twenty thousandths of an inch (0.5 mm), but may also vary depending upon the roadway surface roughness, application specifications, and the type of marking material. Some common liquid marking materials include epoxy, polyurea, traffic paints, or other commonly used marking materials specifically formulated for the roadway marking industry. Examples of roadway marking material manufacturers include Sherwin-Williams of Baltimore, Md. and Epoplex Inc. of Maple Shade, N.J.
Hot thermoplastic material is also commonly used as the roadway marking material. This material is first heated and melted, and then while in a liquefied, molten state, either sprayed (under pressure), ribbon extruded, or applied from a trough or shoe (screed) onto the roadway surface. Cold preformed sections (usually three feet or 91 cm in length) of thermoplastic can also be placed into position along the desired roadway mark path and then semi-liquefied with a torch. The semi-liquefied thermoplastic material first conforms to the roadway surface and then quickly cools and solidifies, binding to the roadway surface forming the desired roadway mark.
Another material used for roadway marks is supplied in tape form. The specially formulated roadway marking tape is the actual roadway mark in continuous flexible form having an adhesive coating on the bottom surface for affixing the roadway marking tape to the roadway surface. This product may be directly applied on the top surface of the roadway surface, inlaid directly into hot asphalt roadway surfaces, or preferably applied into a groove which has been previously milled into the roadway surface. An example of a continuous roadway marking tape product is Stamark™ Pavement Marking Tape manufactured by the 3M Company of St. Paul, Minn.
All of the above roadway mark materials are effective for visibly defining the roadway lane demarcation marks during daytime and clear weather conditions, but are less effective during wet and nighttime conditions.
To increase the wet and nighttime visibility of the roadway mark, reflective elements are applied onto the roadway mark material during the application process. These reflective elements reflect the on-coming headlights of an approaching vehicle back towards the approaching driver greatly improving nighttime visibility of the roadway mark. Reflective elements may be dispensed onto the top surface of either the freshly sprayed roadway marking or the melted thermoplastic to further improve the nighttime visibility of the roadway markings. Tape products may also integrate the reflective elements into the tape surface forming a composite reflective surface.
The most common reflective elements which are co-applied with the liquid or thermoplastic roadway marking material are small and generally spherically shaped glass beads. The beads are constructed so that they will efficiently back-reflect light from oncoming headlights thus self-illuminating the roadway mark. The term “retro-reflectivity” is used to describe this phenomenon.
For liquid-based sprayed materials, beads are commonly dispensed with a velocity equal and opposite that of the forward moving paint truck so that the beads fall almost vertically downward under the force of gravity and partially embed themselves onto the top surface of the freshly applied marking material. The top portion of the bead is exposed and thus able to retro-reflect the oncoming vehicle headlights.
The size of roadway beads varies but the most common bead diameters range from approximately fifteen to fifty thousandths of an inch (0.4 to 1.2 mm). A popular manufacturer of roadway marking glass beads is Potters Industries LLC of Malvern, Pa.
As the liquid marking material dries, cures, or in the case of liquefied (molten) thermoplastic, cools and solidifies, the beads are in effect glued and affixed to the marking material and hence to the roadway surface. The marking material (often referred to as the binder) along with the imbedded beads form a hard composite structure having a rough raised and exposed top surface. The exposed portion of the bead above the cured binder captures and back reflects part of the on-coming light from vehicle headlights. The thickness of the finished roadway marking includes the thickness of the hardened binder along with the exposed portion of the bead above the cured liquid material surface.
Beads of two or more different diameters may also be simultaneously dispensed together to achieve different reflectivity properties for different environmental roadway conditions. Other non-spherical reflective elements may also be dispensed singularly or in combination with other types of reflective elements.
For example, twenty thousandths inch (0.5 mm) diameter beads may be co-dispensed with fifty thousandths inch (1.25 mm) diameter beads to better improve wet (rainy) nighttime roadway reflectivity. Dispensing two different types of reflective components is commonly referred to as a double drop process. Dispensing three types of reflective components (for example, two different sized beads and one irregularly sized reflective element) is referred to as a triple drop process.
A portion of the larger diameter bead may be able to protrude above the wet film thickness of the water on a wet roadway surface and still retro-reflect light from oncoming headlights. Because the larger diameter beads protrude significantly above the road surface, however, they are more susceptible to degradation over time. In contrast, the smaller diameter beads may be completely submerged under the wet film thickness of the water on a wet roadway surface and will not effectively capture, and therefore not back-reflect, the light from oncoming headlights, but because of their smaller size, are less susceptible to degradation over time. Other irregular shaped and dimensioned reflectivity elements are sometimes additionally dispensed along with beads to further improve roadway marking reflectivity under wet roadway conditions.
For roadway mark material supplied in tape form, the reflective elements are usually directly integrated into the tape and form a continuous composite structure. Some tape products have reflective elements that are imbedded in a polygon-shaped, raised profile arranged in a waffle-like pattern to capture and back-reflect the light from oncoming vehicle headlights for both dry and wet nighttime conditions.
All of the above solutions are effective in producing initially high-contrast differentiation between the roadway marks and the roadway surface under different environmental driving conditions. This initially high contrast differentiation tends to degrade over time, however, for various reasons. For example, the actual binder material which defines the visible reflective shape of the roadway mark (usually rectangular shaped) may become worn with vehicular traffic and the passage of time, and may further become discolored because of lengthy exposure times to ultra-violet radiation from the sun. Further, black tire scuff marks may occur on the surface of the roadway mark further degrading mark visibility.
Differences in the coefficients of thermal expansion between the binder material and roadway surface may also cause a physical separation between them further degrading the ability to maintain a consistently visible roadway mark. Seasonal roadway temperature variations over time may cause cracking and peeling of the roadway mark further degrading the effectiveness of the marking.
The reflective elements for the liquid, thermoplastic, and tape applications which are installed along with their respective binder may wear away quickly as the result of frictional contact between the tires of passing traffic and the applied roadway mark. Roadway mark degradation also occurs as the result of the partial or complete scraping removal of the binder and its reflective beads or reflective elements from plows attempting to clear the roadway surface of snow in northern climates. Usually the exact positions of the roadway lanes, and therefore the roadway marks defining those lanes, are not visible during the snow-plowing process thereby increasing the probability that the marks will be accidentally scraped and removed by the plow.
To maintain effective contrast between the roadway mark and roadway surface, roadway transportation agencies and others may periodically employ different roadway mark reapplication processes to maintain roadway mark contrast and visibility. One process first removes the worn pre-existing mark by specialized grinding machines (commonly called “grinding trucks”) or with a pressurized and circulating stream of water (commonly called “water blasting”). A new roadway mark is then reapplied onto the bare roadway surface at approximately the same position where the original mark existed. This particular reapplication process is costly and inefficient because it requires use of a dedicated and expensive piece of equipment (commonly referred to as a “grinding truck” or a “water blaster”) or a combination of marking-removal machines, to first remove the pre-existing worn lines, and then additional time and labor costs are required to again lay out a new roadway mark path and apply the new roadway marking. Furthermore, the motoring public is inconvenienced as the result of traffic lane closure for both the removal and the subsequent layout and reapplication of the roadway marks.
Another more popular and less expensive reapplication process applies new roadway mark material (for example paint and, if required, reflective elements) directly on top of the pre-existing roadway mark without removing the worn pre-existing roadway mark. This process of reapplying roadway mark material directly on top of the pre-existing roadway mark is commonly referred to as “maintenance striping,” and is the subject of this invention. Common maintenance striping processes may include a completely manually controlled process, or the completely manually controlled process may be partially automated. Both types of maintenance striping processes are now discussed.
For the completely manually controlled maintenance striping process, a driver first positions the paint truck along the pre-existing roadway mark path and then forwardly moves the truck in a longitudinal direction along the mark path at a speed consistent with the roadway mark material dispensing application process. Having a clear frontal perspective view of the pre-existing roadway mark, the driver maintains the paint truck position and truck path substantially parallel with the pre-existing roadway mark path.
As the paint truck proceeds along the pre-existing roadway mark path, a first operator situated towards the rear of the paint truck and having an unobstructed view of the pre-existing roadway mark controls the lateral position of the roadway mark material dispensing hardware (usually a moveable carriage more fully described below) and process on one side of the paint truck (for example, the left side for painting a center line in the United States). A second operator may also be stationed towards the rear of the paint truck for controlling the roadway mark dispensing hardware and process on the opposite side of the paint truck (for example, the right side for painting a lane edge line). These operators are responsible for both properly aligning the material dispensing hardware over the pre-existing roadway mark and also for controlling the timing of when to begin, and when to end, the dispensing of the roadway mark material.
For long lengths of solid line roadway mark dispensing (such as roadway center lines), the operators are primarily concerned with only aligning the dispensing hardware over the pre-existing mark and are not so concerned with continuously controlling the timing of when to begin, and when to end, the dispensing of the roadway mark material except at the beginning and end of the solid line mark. This is not the case, however, for repetitive skip line patterns where the operators must continuously align the dispensing hardware over the pre-existing roadway mark and simultaneously monitor and adjust the paint truck dispensing system to insure that the newly applied marking accurately reproduces the existing skip line pattern by periodically manually correcting the timing of when to begin, and when to end, the dispensing of the roadway mark material.
Manual maintenance striping of a roadway mark therefore requires a driver to steer and align the paint truck along the pre-existing roadway mark path and at least one and possibly two operators for controlling both the lateral position of the roadway mark dispensing hardware and timing of when to begin, and when to end, the dispensing of the roadway mark material.
The dispensing hardware for liquid (or other types) of mark material (for example, an epoxy binder) usually consists of two laterally extendable and hydraulically controlled carriages mounted on opposite sides of the paint truck. Left and right side carriages are usually provided so that the center and side lines may be painted (either singularly or simultaneously) as the paint truck moves along the roadway mark path, and are controlled by their respective operators. The carriages further have attached and downwardly directed guns which spray the roadway mark binder material (for example, paint) onto the roadway surface. Reflective media dispensing guns may also be affixed to the carriage rearward of the roadway mark binder spray guns. Other roadway mark materials may require different dispensing hardware which is compatible with the particular roadway mark material.
The hydraulic control system for each carriage may include a conventional hydraulic steering control unit which cooperates with one or more hydraulically operable cylinders having a moveable piston (which is further attached to a piston rod) for laterally extending and retracting the carriage (one end of the cylinder is fixed to the paint truck body and the piston rod is attached to the carriage). The hydraulic steering control unit controls the direction of hydraulic fluid to the hydraulic responsive piston which in turn either laterally extends or retracts its respective carriage.
The operators manually control the lateral position and movement of the left and right side mounted carriages (and therefore the liquid binder and bead gun lateral positions) by controllably rotating the hydraulic steering control unit via a conventional steering wheel. Turning the steering wheel in one direction may extend the carriage while turning the steering wheel in the opposite direction may retract the carriage, with the lateral velocity of the carriage determined by how quickly the operator can physically turn the steering wheel.
The hydraulic carriage control system allows the respective operators to laterally align the roadway mark material dispensing hardware over the pre-existing roadway mark path and to adjust the carriage position to account for slight positional inaccuracies of the driver in positioning the paint truck when attempting to follow the roadway mark path, especially around curved roadway mark paths.
Having aligned the guns at the correct lateral position with the pre-existing roadway mark path, the operator must then decide when to begin and when to end the dispensing of the roadway mark material as the paint truck proceeds along the pre-existing roadway mark path. Usually the operator attempts to start dispensing mark material at the beginning edge of the pre-existing line segment. To accomplish this task, the operator must first visually locate the leading edge of the line segment and then estimate when to begin dispensing the roadway mark material taking into consideration the inherent turn-on delay of the dispensing valves and vehicle speed. Variations in both truck speed, dispensing valve turn-on delay, and operator response time usually result in positional misalignment between the actual beginning, or leading edge, of the pre-existing roadway mark line segment and the starting edge of the newly applied mark line segment. A positional alignment tolerance between the actual leading edge of the pre-existing roadway mark line segment and the starting edge of the newly applied mark line segment is usually allowed by most transportation agencies or others responsible for maintaining roadway markings. A mark edge positional tolerance may be plus or minus a number of inches (or centimeters) and can vary according to a particular transportation agency or other defined specification.
Having started dispensing the roadway mark material on top of the pre-existing mark, the operator continues to dispense the roadway mark material until the trailing edge of the pre-existing mark line segment comes into view, at which time the operator attempts to judge the proper time at which to stop the dispensing process. Trailing edge positional errors between the pre-existing mark and the newly applied mark may occur because of variations in truck speed, dispensing valve turn-off delays, and operator response time. Slower vehicle speeds may be necessary to give the operators more time to determine when to begin, and when to end, the dispensing of mark material thereby minimizing the leading and trailing mark edge positional alignment errors. A slower moving truck increases the amount of time necessary, however, to re-apply the mark material over the pre-existing mark.
Although successful in dispensing new roadway mark material on top of a pre-existing roadway mark, the manual process is prone to human error based upon the fact that the operator must simultaneously laterally align the dispensing hardware and control the timing when to begin and end the dispensing of mark material.
In addition, the operator cannot accurately determine the actual length of the line segment and will usually dispense new roadway mark material over the entire length of the visible pre-existing line segment without regard to the original line segment specification. For example, a common 15/40 skip-line pattern should include a 15 foot (450 cm) line segment with a 25 foot (750 cm) gap. Because of previous restriping activities, however, the 15 foot (450 cm) line segment may have been over sprayed and lengthened to a 17 foot (520 cm) line segment. With a manually controlling restriping process, the operator may overly dispense and restripe the entire 17 foot (520 cm) line segment even though the original specification calls for a 15 foot (450 cm) line segment, thus unnecessarily wasting a good percentage of roadway mark material. Alternately, the operator may short-dispense the line segment of a skip-line pattern. For example, if the required 15 foot (450 cm) paint line segment was previously under sprayed to a length of 13 feet (400 cm), the operator may only restripe the previous most recent and visible 13 foot (400 cm) line segment (the remaining 2 foot (60 cm) line segment of the original 15 foot (450 cm) line segment being worn away).
In an attempt to minimize the edge positional errors and to stripe the specified line segment length, “timer-based” controller systems have been created to assist the operator during the restriping process. These partially automated systems typically determine the distance travelled by the paint truck along the roadway mark path and use this information to appropriately turn-on and turn-off the paint guns (or other roadway mark material dispensing apparatus, including, for example, bead dispensing systems) to create the desired skip-line pattern. An example of a commercially available system for controlling the dispensing of roadway mark materials is model SM-5 manufactured by Skip-Line Inc. of La Grande, Oreg.
The distance travelled by the paint truck may be determined from a drive shaft-mounted aluminum ring having a number of permanent magnets imbedded around the outer circumference of the ring. As the drive shaft (and hence the attached ring) rotates, the spatially changing permanent magnetic flux is detected by a chassis-mounted conventional Hall-effect sensor or other magnetically responsive sensor which outputs a series of electrical pulses. For example, having twenty permanent magnets imbedded in the ring will produce twenty pulses for each drive shaft rotation. Because drive shaft rotation also causes rear wheel rotation via the rear axle and differential, the number of pulses produced at the drive shaft location will be proportional to the rear wheel rotation, and hence proportional to the linear distance travelled by the vehicle. The equivalent linear distance travelled per pulse is usually first determined by a calibration procedure before a roadway is restriped.
To calibrate the system, the driver will first physically measure a known length of roadway (for example, 1,000 feet or 300 m). The truck is then driven along this known length of roadway and the number of pulses produced by the magnetically responsive sensor is recorded by the timer. Knowing the distance travelled (in feet or other convenient length unit) and the number of corresponding pulses produced for this distance by the magnetically responsive sensor allows the system to calculate the equivalent linear distance (feet) travelled per pulse, and which may also be used to calculate vehicle speed in miles per hour (feet per pulse*pulses per second*3,600 seconds per hour*1 mile per 5,280 feet). The distance travelled by the paint truck may then be determined by counting the number of pulses and can therefore be used to determine an accurate line segment and gap lengths for dispensing the roadway mark material.
For example, after completing the calibration procedure, one pulse from the magnetically responsive sensor may correspond to a travelled distance of 1.2 inches (30 mm). Assuming a 15/40 skip line is to be restriped, the controller would turn-on the valves to dispense roadway mark material for 150 pulses ((15 feet*12 inches per foot)/(1.2 inches per pulse)) and subsequently turn-off the valves thereby not dispensing the roadway mark material for 250 pulses. This turn-on and turn-off cycling of the dispensing valves would be repeated for the entire length of the skip line. The controller may also compensate for the turn-on and turn-off delay times of the dispensing valves, and other timing advance or delay issues.
Assuming the calibration distance to pulse ratio is constant throughout the restriping process, these types of controllers can repeat the painted line segment and gap lengths with good positional accuracy.
The distance to pulse ratio may change, however, during the restriping process. For example, it is well known that tire diameter is a function of tire pressure, and that tire pressure is a function of tire temperature. Variations in tire temperature can therefore cause changes in the diameter of the tire which subsequently changes the previously calibrated distance to pulse ratio. For example, increases in tire temperature during the restriping process may cause a change in tire pressure. This change in tire pressure may result in a change in tire diameter which may result in a distance error per tire revolution. Besides the change in temperature ultimately affecting the distance travelled per tire revolution, the operators may decide not to recalibrate the distance-to-pulse ratio before beginning a new painting application but instead rely upon previous distance-to-pulse values. Other factors may also affect the distance travelled per tire revolution such as tire wear and tire deflation caused by leaking or inoperable tire valves.
Errors caused by changes in the distance-to-pulse ratio during the restriping process, or by using previous and not current ratios, are cumulative and cause positional errors in the painted line segment and gap lengths. For example, assuming a 15/40 skip line is to be restriped and assuming an initial 1.2 inches (30.5 mm) per pulse ratio, a change from 1.2 inches (30.5 mm) per pulse to 1.25 inches (31.75 mm) per pulse would produce a skip line mark of 15.625 feet (476 cm) and not the desired 15 foot (457 cm) long skip line mark, a difference of 7.5 inches (19 cm). The gap length will also change from 25 feet (762 cm) to 26.04 feet (792 cm), a difference over one foot (30 cm). This dispensing cycle error is cumulative and continues throughout the restriping process, and if not quickly corrected results in an unacceptable restriped roadway mark pattern.
To adjust the dispensing cycle to account for slight variations in positional dispensing of the roadway mark material caused by the errors in the distance-to-pulse ratio or other errors, the operators visually observe the beginning position of where the roadway mark material is being dispensed and visually compare this position with the beginning position of the pre-existing roadway mark. If the start position of the dispensed roadway mark is not aligned with the start position of the pre-existing mark, the operators must manually lead (advance) or lag (delay) the timing of when to dispense the roadway mark material (commonly referred to as jogging) to realign subsequent start positions.
The accuracy of restriping exactly over the pre-existing roadway mark is greatly dependent upon the ability of the material-dispensing operators to both laterally align the carriage (and therefore the dispensing hardware, i.e., the paint-spraying guns) over the roadway mark as the paint truck moves along the roadway mark path, and further to advance or delay the dispensing starting position of the roadway mark material to account for any variations in the distance-to-pulse ratio and other factors. The positional accuracy of the partially automated restriping process is therefore dependent upon the accuracy and consistency of the calibration procedure and again on the judgment of the material-dispensing operators, and therefore is prone to errors.
Furthermore, the requirement that the operators have an unobstructed view of the roadway mark for both laterally aligning the carriage over the roadway mark and for advancing or delaying the timed dispensing cycle usually places the operators towards the rear of the paint vehicle and therefore in harm's way of high speed passing or common lane traffic. Documented operator injuries have occurred because of collisions between the rear portion of the paint truck and passing or common lane traffic.
Previous attempts to completely automate the maintenance restriping of pre-existing roadway marks have particularly included systems which use the optical characteristics of the previously applied roadway mark material for controlling the lateral position of the mark material guns and the actual timing of when to begin and end the application of mark material.
For example, U.S. Pat. No. 3,101,175 issued to Carl F. Brown teaches a paint truck having a closed circuit television system which is used to assist the paint truck driver in guiding the vehicle along the roadway mark path. The driver of the truck must carefully position the vehicle adjacent to the pre-existing roadway mark and, using the television image of the pre-existing roadway mark, attempt to steer the paint truck to continuously align the roadway mark dispensing hardware over the pre-existing roadway mark. The driver must continuously monitor the television receiver to maintain the dispensing hardware alignment over the pre-existing mark position in addition to controlling when to start and stop the dispensing of roadway mark material. Although this patent attempts to eliminate the operator from the rear of the paint truck, maintaining an accurate dispensing position over the pre-existing roadway mark is difficult because of the simultaneous tasks required of the driver to properly dispense the roadway mark material at exact times while maintaining both the truck and roadway material dispensing hardware alignment with the current roadway mark path, and also attempting to control the position of the paint truck along the pre-existing roadway mark path.
U.S. Pat. No. 3,229,660 issued to J. L. McLucas et al. teaches an apparatus for selectively applying roadway marking material to highway pavements and also for automatically controlling a paint-applying vehicle along a predetermined roadway mark path. Information-bearing signal elements placed beneath or on top of the roadway surface define a predetermined roadway mark pattern. The information-bearing elements may include strips of metal or radioactive material embedded into the roadway surface, or the previously affixed and optically responsive roadway mark material (paint). Detectors responsive to the respective information-bearing elements control dispensing new roadway mark material. A photocell is disclosed for detecting the presence of a painted roadway mark. A signal is generated when a roadway mark is detected which is then used to control the dispensing of mark material. The optical detectors work well assuming that there is sufficient roadway marking material available on the roadway surface for the photocell to optically distinguish between a marked and unmarked surface. This situation rarely occurs because traffic has diminished the optical distinguishing characteristics of the previously applied mark or has completely removed the mark from the roadway surface. The invention is therefore capable of applying mark material only at those positions where sufficient previously applied roadway mark material is currently optically detectable.
U.S. Pat. No. 5,054,959 and No. 5,169,262 issued to Wilson et al. teach a pavement line marking apparatus which comprises a support structure mounted to a moving paint truck having a marking detector (line scan camera) for detecting an old line marking, a transversely moveable and controllable paint applicator for depositing paint onto the old line marking, and a control system responsive to a signal from the marking detector to move the paint applicator into a position over the old line marking and to controllably deposit paint onto the old line marking. These apparatus work well if the old line marking is detectable by the marking detector but fail if some of the old line marking has been completely obliterated along the current roadway mark path. Further, if the beginning of the line mark is not clearly identified by the marking detector, the paint will not be deposited until the beginning of the line mark edge is clearly identified by the mark detector.
U.S. Pat. No. 5,203,923 issued to William H. Hartman teaches a control system for repainting old paint markings comprising a source of light which illuminates and electromagnetically stimulates the pre-existing roadway mark. A spectroscopic detector analyzes the spectral content of the reflected light from the pre-existing roadway mark to determine the presence or absence of known preselected chemical constituents of the mark material for both controlling roadway mark material dispensing and for tracking the roadway mark path. Reliable detection of the roadway mark requires, however, that the electromagnetic spectral emission response of the chemical constituents of the roadway mark material be matched with the wavelength of the illumination to achieve the greatest amount of stimulated (fluorescence) spectral emission, and if the mark is worn away by traffic it no longer provides stimulated emission.
U.S. Pat. No. 5,456,548 issued to Smyrk et al. discloses an apparatus for applying lines of pre-existing roadway mark configurations onto a roadway or pavement surface and to accurately repeat the roadway mark patterns. The apparatus comprises a survey system mounted near the front of the paint vehicle having a roadway mark detector (a charge-coupled device, or “CCD,” line scanning camera) to transversely scan the roadway surface, and a pattern transition detector taught by a neural network to recognize line pattern changes, and in response thereof, control the dispensing of mark material to accurately repeat the line pattern changes. The accuracy of the apparatus in determining the exact point at which a transition occurs between the current line pattern and a following line pattern (for example a mark and skip pattern), and therefore the dispensing of roadway mark material, depends upon how well the neural network is able to learn from the various pattern changes.
Although current maintenance striping technology using the optical characteristics of the previously applied roadway mark material for controlling the dispensing of roadway mark material has been partially successful, further improvements to the prior art may be made to more fully automate and increase the accuracy and speed of the restriping process and eliminate the carriage operator or operators from the rear of the vehicle, thus requiring only one operator (the driver of the paint vehicle) to complete the restriping process.
For example, an apparatus to fully automate the restriping process should (1) automatically and accurately align the roadway mark material dispensing gun(s) at the beginning edge location of the first mark of the first striping cycle and the beginning edge locations of subsequent marks throughout the restriping process; (2) automatically and accurately dispense roadway mark material over the pre-existing roadway mark(s); (3) accurately maintain mark and gap lengths for each skip-line cycle; (4) automatically dispense roadway mark material (including the binder material and reflective components) for single, double, or shadow (contrast) line applications; (5) monitor the dispensing process of roadway mark materials; (6) be easily installed and retro-fitted to existing line-striping vehicles, and particularly for line-striping vehicles having a manually controlled hydraulically operated carriage positioning system; (7) automatically determine the desired skip-line pattern; (8) automatically self-calibrate the distance-to-pulse ratio during the restriping process; (9) reduce errors in determining the distance-to-pulse ratio; and (10) improve the start and ending positional alignment between the newly applied and pre-existing roadway marks, with or without the pre-existing roadway mark being optically detectable. Other improvements will become apparent in view of the present invention.
None of the prior art addresses all of these requirements. Thus, there is a need in the roadway marking industry for a roadway mark maintenance striping apparatus that requires less manual labor, increases operational safety for the operators, is more accurate and efficient and less expensive than the current roadway maintenance striping technology available today.